The present invention relates to waste traps for patient monitoring devices such as capnometers, and more particularly to apparatus for promoting waste-free primary flow in such waste traps as well as such devices in general.
Certain patient monitoring devices include gas/waste separators for separating a desired, to-be-analyzed gas mixture from waste material such as sputum and spittle. One such device that includes a separator is a capnometer. Capnometers are used to measure the percentage of CO.sub.2 in a patient's breath. Examples of such capnometers and separators are disclosed in U.S. Pat. No. 4,579,568 to Ricciardelli and Blazel, U.S. Pat. No. 4,592,368 to Ricciardelli and Sommer, and U.S. Pat. No. 4,713,095 to Ricciardelli, each of which is incorporated herein by reference.
As is known to those skilled in the art and as described in the above patents, conventional capnometers are designed with a channel that conducts a patient's breath sample from a mouthpiece to a gas/waste separator. Coupled to the separator are two channels for conducting gas/waste.
One such channel is called the primary, or gas-sensing channel and the other, the secondary channel. The channels may be designed so that either a single pump or dual pumps maintain negative pressure in both channels. If a single-pump design is used the secondary channel is called the blow-down channel. As used herein, secondary channel means the non-gas-sensing channel of a capnometer whether or not such channel is a blow-down channel or a secondary channel.
The gas-sensing channel is designed to conduct a relatively high percentage of the patient's breath, referred to herein as the gas-sensing or primary flow, from the separator to a gas-sampling chamber. The gas-sampling chamber will be referred to herein as an optical bench, or bench.
The secondary channel is designed to conduct a relatively small percentage of the patient's breath from the separator through a waste trap, and through a pump where it exits the capnometer.
Conventional separators such as those described in the above patents include three ports. A first port is for receiving a patient sample conducted from the patient airway; a second port is for allowing gas to be conducted to the optical bench; a third port is for allowing waste to be conducted to the waste trap.
Secondary flow begins where gas, and waste, flow from the separator into the waste trap through a suitable port. Then, as long as nothing obstructs secondary flow, gas flows through and out of the trap via a suitable port while waste remains in the trap.
As described and exemplified in the above patents, several proposals have been made concerning improvements to the separator in conventional capnometers.
However, until now, no one has proposed apparatus for promoting waste-free primary flow during a measurement cycle before the waste trap becomes full.
As is known to those skilled in the art, secondary flow is necessary to ensure that proper gas/waste separation will take place in the separator. Proper separation is extremely important because, in its absence, waste will enter and contaminate the primary channel including the optical bench, thus ruining the desired gas measurement. In addition, substantial cost will be incurred by having to dismantle the capnometer to clean contaminated components.
Conventional capnometer waste traps do not promote waste-free primary flow for several reasons. First, traps such as those disclosed in U.S. Pat. No. 4,579,568 to Ricciardelli and Blazel, U.S. Pat. No. 4,592,368 to Ricciardelli and Sommer cannot operate in all orientations. That is, the traps disclosed therein allow undesired waste flow into the secondary channel from the trap if they are tilted or inverted during use.
Likewise, U.S. Pat. No. 4,886,528 to Aaltonen et al. discloses a trap with a water separator positioned in a secondary channel downstream of the trap, but such apparatus is not operable in all orientations. That is, the trap will allow undesired waste flow into the water separator if the trap is tilted/inverted during use. Such waste flow may block gas-flow through the separator, thus blocking secondary flow.
It is undesirable to allow waste in the secondary channel because it could foul the pump or tubing. Even worse, waste could block secondary flow causing improper or faulty gas/waste separation in the separator. Improper/faulty gas/waste separation results in waste entering the primary flow which ruins desired gas measurement and contaminates the optical bench.
It is therefore an object of the present invention to provide apparatus for promoting waste-free primary flow in a patient monitoring device during a measurement cycle.
A further object of the present invention is to provide apparatus for preserving secondary flow in a patient monitoring device during a measurement cycle.
Another object of the present invention is to provide a waste trap for conventional patient-monitoring devices that preserves secondary flow independent of the orientation of the trap.
Yet another object of the present invention is to provide means for monitoring the volume of waste in the trap during the measurement cycle and for sending signals to conventional control circuitry that is designed to activate associated conventional audible/visible alarm devices upon receiving a threshold signal. Such monitoring/sending means would thus promote waste-free primary flow and preserve secondary flow by letting the user know when the trap is nearly full and ready to be emptied.